(19)
(11) EP 0 490 397 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
14.04.1993 Bulletin 1993/15

(43) Date of publication A2:
17.06.1992 Bulletin 1992/25

(21) Application number: 91121396.5

(22) Date of filing: 12.12.1991
(51) International Patent Classification (IPC)5: G02B 27/00
(84) Designated Contracting States:
DE FR GB IT SE

(30) Priority: 14.12.1990 US 627783

(71) Applicant: Hughes Aircraft Company
Los Angeles, California 90045-0066 (US)

(72) Inventors:
  • Moss, Gaylord E.
    Marina del Rey, California 90291 (US)
  • Wreede, John E.
    Azusa California 91702 (US)
  • Yu, Kevin
    Temple City, California 91780 (US)
  • Scott, James E.
    Hermosa Beach, California 90254 (US)

(74) Representative: Grünecker, Kinkeldey, Stockmair & Schwanhäusser Anwaltssozietät 
Maximilianstrasse 58
80538 München
80538 München (DE)


(56) References cited: : 
   
       


    (54) Guard holograms


    (57) A head-up display for a vehicle, including a primary image reflection hologram (11) supported by a transparent substrate located in the vehicle operator's field of view for the ambient scene in front of the vehicle, a light source (17) for providing playback illumination to the primary image hologram, and a guard hologram (13) in front of the primary image hologram (11) for substantially reflecting ambient illumination that otherwise could spuriously turn on the first reflection hologram, the guard hologram (13) having an angular bandwidth and a spectral bandwidth that are greater than the angular bandwidth and the spectral bandwidth of the primary image hologram, and having an optical density of 2.0 or greater. The guard hologram can be parallel fringe reflection hologram or a slant fringe reflection hologram.






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